1. Field of the Invention
The present invention relates to a display device, and more particularly, to a laser display device and a method for controlling the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for controlling a phase of a laser beam, so as to eliminate a speckle effect from a screen displaying a projected image, thereby clarifying image on the screen for the viewers.
2. Discussion of the Related Art
The projection display device is a display device whereby a small screen is enlarged and projected to display large-sized screen. Generally, among a wide range of projectors, mostly consisting of a light source and a illumination part enlarging and projecting a film and picture image on a screen, a projector adopting a cathode ray tube (CRT) is most widely used. However, recently, projectors having a liquid crystal display mounted thereon are being supplied more increasingly.
In addition, such projectors can be connected to a personal computer or a video tape recorder (VTR), so as to be applied for viewing movies or carrying out various types of presentations through a wider screen.
Meanwhile, the projection display device using a lamp as a light source is disadvantageous in that the color tone, resolution, range of color representation, and contrast of the picture image are lower than those of other self-emissive display devices.
Accordingly, a laser display device using a light amplification by simulated emission radiation (LASER), hereinafter referred to as a “laser”, has been developed in order to resolve such problems.
By using a laser light source, the laser display device can display an image having a high color resolution and an excellent color representation very close to the natural colors. Also, due to the high contrast of the laser display device, an image of an excellent high-resolution picture quality can be represented.
FIG. 1 illustrates a structure of a general laser display device.
Referring to FIG. 1, the laser display device consists of a laser light source 11 generating a laser beam, a illumination optical part 12 irradiating the laser beam generated from the laser light source 11 to an image display device 13, an image display device 13 displaying a picture image by using the irradiated laser beam 11, a projection optical part 14 enlarging and projecting the image displayed in the image display device 13, and a screen 15 on which the image enlarged by the projection optical part 14 is formed.
Herein, since the laser light source 11 generates a single-colored light beam, a red (R) laser light source, a green (G) laser light source, and a blue (B) laser light source are required in order to represent a color image.
The laser light source 11 uses a radiation of the internal energy of a matter, so as to generate light energy, which is then amplified. When generating a constant light energy, the laser light source 11 should use a gas laser light source, such as carbon dioxide. Conversely, when generating a large amount of spontaneous light energy, then the laser light source 11 should use a solid-state laser light source, such as ruby.
A semiconductor laser light source using arsenic (As) or gallium (Ga) can also be used.
However, unlike natural light, the light generated from the laser light source 11 generates coherent waves having the same frequency and phase.
Due to the characteristics of coherence in a laser, a laser disturbance occurs on the screen, thereby causing a speckle effect, which is an optical interference causing grainy white spots sparkling on the screen. The speckle effect decreases the contrast and resolution, thereby deteriorating the picture quality of an image.